Most erythema multiforme is associated with herpes simplex or mycoplasma infections.

The exact cause is unknown. The disorder is believed to involve damage to the blood vessels of the skin, followed by damage to skin tissues.

Some forms of this condition are more severe than others. Erythema multiforme minor is not very serious. Erythema multiforme major (also called Stevens-Johnson syndrome) is more severe. The more severe form is usually caused by reactions to medications, rather than infections.

Skin grafting may be helpful in cases in which large areas of the body are affected.

In cases that are caused by the herpes virus, daily antiviral medications may be prescribed to prevent erythema multiforme from returning.

Support Groups:

Expectations (prognosis):

Mild forms of erythema multiforme usually get better in 2 - 6 weeks, but they may return. More severe forms may be difficult to treat. Stevens-Johnson syndrome and toxic epidermal necrolysis have high death rates.